‘No evidence’ gene mutation caused Folbigg deaths: US doctor

A US-based professor of medicine and cardiology has told an inquiry into Kathleen Folbigg’s convictions over the deaths of her four children that there is insufficient evidence to conclude a rare genetic mutation caused the deaths of her two daughters.

Calum MacRae, who is based at Harvard Medical School, told the inquiry in Sydney on Friday that there was “a possibility” Sarah and Laura Folbigg died as a result of the variant, but he did not “think any of the evidence [to date] suggests that it’s a reasonable possibility”.

A younger Kathleen Folbigg and her children (clockwise): Patrick, Sarah, Caleb and Laura.Credit:AAP, supplied

“At the moment there’s no evidence one way or the other,” he said via video link.

MacRae provided a report to the inquiry in January and concluded there was “no … evidence presented that would support the identified variants as causal in the death of the Folbigg children”.

Counsel assisting the inquiry, Julia Roy, remarked: “You’ve put that quite unequivocally. There’s no evidence.”

MacRae replied: “No extant evidence that would support that. At present there’s no evidence that would link its pathogenicity [ability to cause disease] one way or the other that has been reviewed.”

Former NSW chief justice Tom Bathurst, KC, who is heading the inquiry into whether there is a reasonable doubt about Folbigg’s convictions, put to MacRae: “You accept, I think, that it’s a possibility that the death was caused as a result of that mutation?”

“Absolutely, I agree with the possibility,” MacRae said, but he maintained that in his view it was not a reasonable possibility.

Folbigg, now 55, is serving a minimum 25-year prison sentence after being convicted in 2003 of the murder of three of her children, Patrick, Sarah, and Laura, and the manslaughter of her first child, Caleb. Each died suddenly between 1989 and 1999 in the family’s Hunter Valley home, aged between 19 days and 18 months.

DNA sequencing and analysis in 2018 and 2019 revealed Folbigg and her daughters shared a novel variant in a gene that produces the calmodulin protein, CALM2.

The variant was not found in Caleb or Patrick. Recent research suggests the variant may cause cardiac arrhythmias – irregular heart rhythms – and sudden unexpected death.

Professor Arthur Wilde, an internationally renowned cardiologist, gave evidence on Thursday that he could not exclude the possibility the mutation caused the girls’ death but he considered it unlikely, “even highly unlikely”.

Professor Edwin Kirk, a clinical geneticist at Sydney Children’s Hospital, said on Thursday that it was “possible” the variant “could have caused the deaths” of Sarah and Laura, but he did not have enough evidence to say it was likely.

But other experts have told the inquiry the variant provides a reasonable explanation for the two deaths.

Those experts include Professor Carola Garcia de Vinuesa, an immunologist and geneticist who co-authored a 2021 journal article that concluded that calmodulinopathy, a life-threatening arrhythmia syndrome, “emerges as a reasonable explanation for a natural cause” of the deaths.

Danish research scientists Professor Michael Toft Overgaard and Professor Mette Nyegaard, who co-authored the article with Vinuesa, have told the inquiry it was likely the girls died because of the variant.

In the absence of another identifiable cause of death, “the presence of that mutation is a very valid explanation” for their deaths, said another co-author, internationally renowned cardiologist Professor Peter J. Schwartz.

The inquiry resumes on Tuesday.

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